Lead- and cadmium-free finely divided glass frit compositions

Abstract

A lead- and cadmium-free glass-frit composition based on a borate glass and containing 4 to 22 mole % La2O3 and 0 to 10 mole % SiO2 as network-forming oxides and B2O3, wherein the molar ratio of B2O3 to La2O3 is at least 3 to 1. The compositions have an alpha in a range between approximately 50.10-7K-1 and approximately 100.10-7K-1 and the start of melting Td in a range between 470 DEG and 670 DEG C.

What is claimed: 
     
       1. A finely divided lead- and cadmium-free glass-frit composition based on a borate glass, said composition consisting essentially of 4 to 22 mole % La 2  O 3  as network-forming oxide, 30 to 80 mole % B 2  O 3 , at least one oxide selected from the group consisting of alkali-metal oxide, alkaline-earth metal oxide, aluminum oxide, zinc oxide, and mixtures thereof in a total amount of 4 to 65 mole %, other oxides other than Al 2  O 3 , ZnO, Na 2  O, K 2  O, CaO and BaO in the amount of up to a total of 10 mole %, and optionally fluoride added in the form of alkali- and/or alkaline-earth fluorides or of Na 3  AlF 6 , wherein the molar ratio of B 2  O 3  to La 2  O 3  is at least 3 and less than 1 mole % SiO 2  and less than 1 mole % Li 2  O. 
     
     
       2. The glass-frit composition according to claim 1, wherein said composition consists essentially of 4 to 22 mole % La 2  O 3 , 50 to 70 mole % B 2  O 3 , 0 to 20 mole % Al 2  O 3 , 0 to 25 mole % ZnO, 0 to 20 mole % Na 2  O, 0 to 10 mole % K 2  O and 0 to 10 mole % CaO and/or BaO, wherein the sum of Al 2  O 3  and ZnO is 10 to 30 mole % and wherein the sum of Na 2  O, K 2  O, CaO and BaO is 4 to 20 mole %. 
     
     
       3. The glass-frit composition according to claim 1, wherein said at least one oxide is Al 2  O 3 . 
     
     
       4. The glass-frit composition according to claim 3, wherein said composition is essentially free of SiO 2 . 
     
     
       5. The glass-frit composition according to claim 1, wherein said composition has a coefficient of thermal expansion, alpha, in a range between approximately 50•10 -7  K -1  and approximately 100 ∘10 -7  K -1  and the start of melting Td in a range between 470° and about 670° C. 
     
     
       6. The glass-frit composition according to claim 1, wherein said composition consists of 4 to 22 mole % La 2  O 3  as network-forming oxide, 30 to 80 mole % B 2  O 3 , at least one oxide selected from the group consisting of alkali-metal oxide, alkaline-earth metal oxide, aluminum oxide, zinc oxide, and mixtures thereof in a total amount of 4 to 65 mole %, and optionally fluoride added in the form of alkali- and/or alkaline-earth fluorides or of Na 3  AlF 6 , wherein the molar ratio of B 2  O 3  to La 2  O 3  is at least 3 and said composition contains less than 1 mole % SiO 2 . 
     
     
       7. The glass-frit composition according to claim 1, wherein said molar ratio of B 2  O to La 2  O 3  is about 11.5. 
     
     
       8. The glass-frit composition according to claim 1, wherein composition consists essentially of 4 to 22 mole % La 2  O 3 , 45 to 75 mole % B 2  O 3 , 0 to 25 mole % Al 2  O 3 , 0 to 30 mole % ZnO, 0 to 25 mole % Na 2  O, 0 to 10 mole % K 2  O and 0 to 10 mole % CaO and/or BaO, wherein the sum of Al 2  O 3 , Zno, Na 2  O, K 2  O, CaO add BaO is 10 to 50 mole %, and at least one oxide other than Al 2  O 3 , ZnO, Na 2  O, K 2  O, CaO and BaO is present up to 10 mole %. 
     
     
       9. A finely divided lead- and cadmium-free glass-frit composition based on a borate glass, said composition consisting essentially of 4 to 22 mole % La 2  O 3  as network-forming oxide, 30 to 80 mole % B 2  O 3 , at least one oxide selected from the group consisting of alkali-metal oxide, alkaline-earth metal oxide, aluminum oxide, zinc oxide, and mixtures thereof in a total amount of 4 to 65 mole %, other oxides other than Al 2  O 3 , ZnO, Na 2  O, K 2  O, CaO and BaO in an amount of up to a total of 10 mole % and optionally fluoride added in the form of alkali- and/or alkaline-earth fluorides or of NA 3  AlF 6 , wherein the molar ratio of B 2  O 3  to La 2  O 3  is at least 3, the amount of Al 2  O 3  is between 0 and 9.43 mole % and the amount of ZnO is between 0 and 15.06 mole % and SiO 2  is less than 1 mole %. 
     
     
       10. The glass-frit composition according to claim 9, wherein said composition consists essentially of 4 to 22 mole % La 2  O 3 , 50 to 70 mole % B 2  O 3 , 0 to 9.43 mole % Al 2  O 3 , 0 to 15.06 mole % ZnO, 0 to 20 mole % Na 2  O, 0 to 10 mole % K 2  O and 0 to 10 mole % CaO and/or BaO, wherein the sum of Al 2  O 3  and ZnO is 10 to 24.49 mole % and wherein the sum of Na 2  O, K 2  O, CaO and BaO is 4 to 20 mole %. 
     
     
       11. The glass-frit composition according to claim 9, wherein the amount of Li 2  O in said composition is less than 1 mole % Li 2  O. 
     
     
       12. The glass-frit composition according to claim 9 wherein said composition is free of SiO 2 . 
     
     
       13. The glass-frit composition according to claim 9, wherein said composition has a coefficient of thermal expansion, alpha, in a range between approximately 50.10 -7  K -1  and approximately 100.10 -7  K -1  and the start of melting Td in a range between 470° and about 670° C. 
     
     
       14. The glass-frit composition according to claim 9, wherein said at least one oxide is Al 2  O 3 . 
     
     
       15. The glass-frit composition according to claim 9, wherein said composition consists of 4 to 22 mole % La 2  O 3  as network-forming oxide, 30 to 80 mole % B 2  O 3 , at least one oxide selected from the group consisting of alkali-metal oxide, alkaline-earth metal oxide, aluminum oxide, zinc oxide, and mixtures thereof in a total amount of 4 to 65 mole %, and optionally fluoride added in the form of alkali- and/or alkaline-earth fluorides or of Na 3  AlF 6 , wherein the molar ratio of B 2  O 3  to La 2  O 3  is at least 3 and said composition contains less than 1 mole % SiO 2 . 
     
     
       16. The glass-frit composition according to claim 9, wherein said molar ratio of B 2  O 3  to La 2  O 3  is about 11.5. 
     
     
       17. The glass-frit composition according to claim 9, wherein said composition consists essentially of 4 to 22 mole % La 2  O 3 , 45 to 75 mole % B 2  O 3 , 0 to 9.43 mole % Al 2  O 3 , 0 to 15.86 mole % ZnO, 0 to 25 mole % N 2  O, 0 to 10 mole % K 2  O and 0 to 10 mole % CaO and/or BaO, wherein the sum of Al 2  O 3 , ZnO, Na 2  O, K 2  O, CaO and BaO is 10 to 50%, and said at least one oxide other than Al 2  O 3 , ZnO, Na 2  O, K 2  O, CaO and BaO is present up to 10 mole %. 
     
     
       18. A finely divided lead- and cadmium-free glass-frit composition based on a borate glass, said composition consisting essentially of 4 to 22 mole % Li 2  O 3  as network-forming oxide, 30 to 80 mole % B 2  O 3 , at least one oxide selected from the group consisting of alkali-metal oxide, alkaline-earth metal oxide, aluminum oxide, zinc oxide, and mixtures thereof in a total amount of 4 to 65 mole %, other oxides other than Al 2  O 3 , ZnO, Na 2  O, K 2  O, CaO and BaO in an amount of up to a total of 10 mole % and optionally fluoride added in the form of alkali- and/or alkaline-earth fluorides or of NA 3  Alf 6 , wherein the molar ratio of B 2  O 3  to La 2  O 3  is at least 3, the amount of Al 2  O 3  is between 0 and 9.43 mole % and the amount of ZnO is between 0 and 15.06 mole % and the amount of SiO 2  is less than 1 mole %, said glass-frit having been prepared by forming a melt of the foregoing components, and quenching said melt to obtain a finely divided glass-frit composition.